It has long been known to etch automobile identification numbers into windshields and other glass surfaces of automobiles for the purpose of deterring theft. Historically, this involved sandblasting as illustrated in U.S. Pat. No. 4,048,918 to Peck or acid etching through a stencil utilizing an impermeable plastic film. Such stencils have been cut using a spark-discharge method as disclosed in U.S. Pat. No. 4,316,766 to Levin et al or a hot die cutting method as disclosed in U.S. Pat. No. 4,415,284 to Floyd. Although these stencil cutting processes work, they are slow and costly and there is no known way to automate their use.
Automation of the preparation of such stencils is of great importance to avoid etching erroneous identification numbers on to automobiles and the like. It has been reported by the General Accounting Office of the U.S. government that as many as seven percent of the vehicle identification numbers entered into the National Crime Information Center database have been incorrect. Inasmuch as the etched indicia are nearly impossible to remove, the use of better verification methods has become necessary. To this end, the National Auto Theft Bureau has recently adopted a standard for vehicle identification for verifying the entry of vehicle identification numbers into data terminals and public domain software has recently become available for utilizing this standard. Consequently, the means for automatically verifying and providing numbers for etching now exist but on for the production of the stencils themselves.
Recently, a method has been devised which is capable of utilizing the available computer software for generating stencils. This system is disclosed in U.S. Pat. No. 4,585,514 to Scallon. The system utilizes a nitrocellulose tissue stencil in association with a mechanical type-shaped hammer for cutting alpha numeric stencils in response to vehicle identification data provided by a computer. Unfortunately, the method used by the system does not reliably produce acceptable identification numbers and is unsuited for etching additional coded information relating to the automobile, such as information in the form of a bar code which can be read into a computer by a bar code reader.